Method of producing shaped metallic bodies having a copper alloy base and a noble metal outer coating



United States Patent "ice METEZGD 0F E RGDUCHNG METALLZQ 3813335 HAVENG A (ZQFPEP; ALLGY BASE ANB A NQBLE METAL QUEER CQATZNG Manirid Breher, Emilienstrasse 15, Piorzheim- Saarinen-berg, Baden wurttemberg, Germany No Brewing. Filed Sept. 28, 1961, Ser. No. 14135 3 6 Qlaims. (G. 143l27) The present invention relates to a method of producing shaped metallic bodies, and more particularly the present inventon is concerned with producing metal articles comprising an alloy body with a metal or alloy coating firmly adhering thereto.

Throughout the specification and claims the term metal is used to denote not only elementa y metal but alloys as well.

It is frequently desired to produce metal articles which consist of a metal or alloy body having the desired shape and mechanical properties, and of a coating, for instance consisting of a noble metal, firmly adhering to the shaped metallic body.

it is Well known that certain dificulties are encountered in shaping metal bodies which prior to such shaping were provided with a coating, for instance of a noble metal. Thus, the thickness of the gold coating of articles produced of gold coated profiled copper flloy wire will frequently vary by more than 190%. This is due to the fact that already during rolling of the plated wire the thickness of the gold layer or coating is changed in an uneven manner. Furthermore, during deformation of the plated Wire, for instance during shaping of the same to form spectacle temples, the varying degree of deformation of specific wire portions will also cause variations in the thickness of the gold layer. Furthermore, due to repeated deformation of the plated wire, usually followed by annealing, the gold layer will become coarse so that in the finished article, particularly in curved areas of small radius, the surface will be rough and uneven. In order to achieve an even smoothness of the gold surface, such curved areas must be subjected to severe polishing and thereby the thickness of the gold layer in these areas will he further reduced.

When it is required during shaping of the plated Wire or the like to cut the same, then the base metal will be exposed and it will become necessary to apply gold to the thus exposed surface portions of the base metal to improve the appearance and corrosion resistance of the article.

In order to overcome the above-'nentioned difiiculties, it has been proposed to form the shaped body of the base metal or alloy only and to apply the gold or the like coating after the article has been shaped. The desired firm adherence of the coating to the shaped body is then achieved by difi usion heating. Such ditiusion heating conventionally has been carried out for a short period of time and at relatively high temperatures, frequently within the softening range of the base metal. To prevent deformation of the article during such diffusion heating, the heating was carried out by immersion of the plated article in a hot salt melt. However, heating of the base metal or alloy to such high difiusion temperatures frequently unfavorably affects the mechanical strength and resiliency of the product.

It has been proposed to apply the gold or the like coating galvanically and to dispense with the difiusion heating, in order to avoid the above discussed ditnculties, however, in this manner it is not possible to achieve the high degree of adherence of the coating which frequently is required of articles which are exposed to corrosion and/ or resilient stresses.

It is therefore an object of the present invention to Patented Nov.

overcome the above-mentioned difiiculties and disadvantages in the production of metal or alloy coated metallic bodies, such asparts of spectacle frames and the like.

it is another object of the present invention to provide a method for producing such coated metallic bodies in a simple and economical manner and so as to achieve firm adherence between the metal coating and the underlying metallic body.

With the above and other objects in view, the present invention contemplates a method of producing shaped metallic bodies of predetermined configuration, comprising the steps of shaping a heat hardenable first metal in unhardened condition and adapted to be hardened by being heated within a first temperature range, so as to form thereof a shaped body of the predetermined configuration, applying to the thus formed shaped body a coating consisting of a second metal adapted to be firmly joined to the shaped body of the first metal by being subjected to a difiusion-causing heat treatment within a second temperature range, the first and second temperature ranges partially overlapping each other so as to define a third temperature range forming part of the first and of the second temperature range, and heating the thusformed metal coated metal body to a temperature Within the third temperature range so as to simultaneously harden the first metal of the shaped body and causing diffusion between the first and the second metal so as to firmly adhere the coating of the second metal to the shaped body of the first metal.

Thus, according to the present invention, metallic articles may be produced of hardenable alloys, particularly heat-hardenable copper alloys, which after final shaping are coated with a layer of a noble'metal, and the coating is then firmly adhered to the alloy body by diffusion heating which simultaneously will also cause heathardening of the alloy body.

In this manner the article is to be heated only once, namely within a temperature range which is suitable for causing adherence of the coating to the base coating by diffusion and also for the heat-hardening of the base coating.

The coating may consist of one or more metals or alloys and preferably the coating is galvanically applied to the base body.

The finished article produced according to the present invention posseses a metal, preferably noble metal, coating of even thickness throughout, which coating firmly adheres to the metallic base body. Due to carrying out the heat-hardening of the article simultaneously with the diffusion heating thereof, the article will have the desired mechanical strength and resfliency.

it is a further advantage of the present method that the shaping of the base metal body is carried out while the material thereof is inrelatively soft, unhardened condition.

Thus, it is possible according to the present invention, to take advantage of the properties of hardenable alloys and at the same time to assure firm adherence of the coating to the base body by simultaneously heat-hardening the base body and causing adherence of the coating by diffusion. In this manner shaped metallic articles are produced which combine the desired mechanical properties with excellent corrosion resistance.

The method of the present invention is particularly well suited for producing spectacle frames and temples from rolled, profiled, heat-hardenable copper alloy Wires which, after shaping, are galvanically gold plated. Thereafter, thu thus-formed article is heated for about thirty minutes at about 500 C., and thereby heat-hardened under simultaneous dilfusion adherence of the gold layer to the copper alloy. The only further step that might v.3 be required is a slight polishing of the thus heat treated article.

By properly choosing the composition of the heat-hardenable alloy of which the base body is to be formed, hardness and resiliency of the finished product can be controlled.

To carry out the above-described method it is necessary to employ so-called heat hardenable alloys, particularly copper alloys. The heat treatment of such alloys is dependent only upon the properties of the alloys and is in no way atfected by the coating metal. Table 1 below gives by way of example only, among others, several alloy compositions used in the practice as well as the heathardening temperature ranges applying thereto.

In utilizing the method of the present invention for producing spectacle frames to which the gold or gold alloy coating is applied chiefly galvanically, the particular kind and composition of the coating is of no importance whatever. Thus, any comercial gold or gold alloy baths may be used for this purpose. Merely such baths have possibly to be excluded from application as cause a large percentage of organic bath substances to be embedded in the deposit, whereby bubbles may be formed during the subsequent heat treatment.

The diffusion heating temperature of the coating metal depends exclusively on the hardening temperature of the base material. Thus, it is possible in the case of the same base material to always apply the same hardening temperature even where the coating metals differ most strongly from one another. If, on the other hand, the same coating metal is applied to different kinds of base metals, the heat-hardening and diffusion heating temperature ranges will vary according to the particular base metal employed.

Table I below gives by way of example only, several base alloy compositions, coating metals and alloys as well as the heat-hardening temperatures or temperature ranges and the average hardening times applying thereto, the latter being dependent only in how far the increase of the technological values caused by the hardening process is intended to be utilized. In other words, the heathardening or diffusion heating temperatures and the entire treating temperature are identical with one another.

Table 1 Hard- Hard- Base Alloy ening ening Coating Metal Range, Time, C. Hrs.

Percent Cu Percent Be 98-983. 1.7-2.0; 325 1-4 Au or Au alloys.

Percent Cu Percent Percent Si Mn 500 8-20 Do. 600 1-16 Do. 400 20 Do. 350-400 12 Do. 400 1 Do.

Percent Cu Percent Percent Si Ni Residue 0. 5-0. 7 1. 7-2. 1 400-70 %2 D0. Residue 0.8-1.0 3.2 .0 400-470 }2 Do.

Between the initial state and the final state obtainable by hardening, the increase in hardness of the above-listed alloys ranges from 70 to 280 HB (Brinell) hardness in the case of the Cu-Si and Cu-Si-Mn alloys, and from 90 to 360 HV (Vickers) hardness in the case of Cu-Be V alloys.

Based upon the above statements, it is without ditiiculty possible to produce shaped metallic bodies in accordance with the method of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range or" equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. In a method of producing a shaped metallic body of predetermined configuration, the steps of shaping a heathardenable copper alloy in unhardened condition, said copper alloy being selected from the group consisting of copper-beryllium alloys, copper-silicon-manganese alloys and copper-silicon-nickel alloys, so as to form of said copper alloy an unhardened shaped body of said predetermined configuration; applying to at least a portion of the thus-formed unhardened shaped body a coating consisting of a metal selected from the group consisting of gold and gold alloys and adapted to be firmly joined to said shaped copper alloy body by being subjected to a diffusion-causing heat treatment; and subjecting the thus-formed metal coated unhardened copper alloy body to heat-hardening including heating at a temperature within the range of between about 350 C. and 600 C. and at which said heat-hardenable copper alloy will be heat hardened and at which simultaneously diffusion between the same and said metal will take place thereby firmly adhering said metal coating to the thus hardened copper alloy body.

2. In a method of producing a shaped metallic body of predetermined configuration, the steps of shaping a heathardenab le copper alloy in unhardened condition, said copper alloy being selected from the group consisting of copper-beryllium alloys, copperrsilicon-manganese' alloys and copper-silicon-nickel alloys, so as to form of said copper alloy an unhardened shaped body of said predetermined configuration; applying to at least a portion of the thus-formed unhardened shaped body a coating consisting of a metal selected from thegroup consisting of gold and gold alloys and adapted to be firmly joined to said-shaped copper alloy body by being. subjected to a ditfusion-causing heat treatment Within said predetermined temperature range; and subjecting the thusformed metal coated unhardened copper alloy body to heat-hardening including heating at a temperature within the range of between about 350 C. and 600 C. and at I coating to the thus hardened copper alloy body.

3. In a method of producing a shaped metallic body of predetermined configuration, the steps of shaping a heat hardenable copper alloy in unhardened condition so as to form thereof an unhardened shaped body of said predetermined configuration; applying to the thus-formed unhardened shaped body a coating consisting of'a noble metal adapted to be firmly joined to said shaped body of said copper alloy by being subjected to a diffusioncausing heat treatment; and subjecting the thus-formed noble metal-coated unhardened copper alloy-body to heathardening including heating at a temperature within the range of between about 360 C. and 600 C." and at which said heat-hardenable copper alloy will beheat hardened and at which difiusion between said copper alloy and said noble metal will take place, thereby firmly adhering'said coating of said noble metal to said shaped body of said thus-hardened copper alloy.

4. In a method of producing a shaped metallic body of predetermined configuration, the steps of shaping a heathardenable copper alloy in unhardened conditionso as to form'thereof an unhardened shaped body ofsaid predetermined configuration; applying to the thus-formed unhardened shaped body a coating consisting of a noble metal adapted to be firmly joined to said shaped body of said copper alloy by being subjected to a diffusioncausing heat treatment; and subjecting the thus-formed metal-coated unhardened metal body to heat-hardening including heating at a temperature within the range of between about 350 C. and 600 C. and at which said copper alloy will be heat-hardened and at which diffusion between said copper alloy and said noble metal will take place, thereby firmly adhering said coating of said second metal to said shaped body of said thus-hardened first metal.

5. In a method of producing a shaped metallic body of predetermined configuration, the steps of shaping a heathardenable first metal consisting of a copper alloy in unhardened condition so as to form thereof an unhardened shaped body of said predetermined configuration; galvanically applying to the thus-formed unhardened shaped body a coating consisting of a noble metal adapted to be firmly joined to said shaped body of said first metal by being subjected to a diffusion-causing heat treatment; and subjecting the thus-formed metal-coated unhardened metal body to heat-hardening including heating at a temperature within the range of between about 350 C. and 600 C. and at which said first metal will be beathardened and at which diffusion between said first and said noble metal will take place, thereby firmly adhering 6. In a method of producing a shaped metallic body of v predetermined configuration such as spectacle temples and the like, the steps of shaping a heat-hardenable copper alloy in unhardened condition so as to form thereof an unhardened shaped body of said predetermined configuration; galvanically applying to the thus-formed un hardened shaped body a coating consisting of a noble metal adapted to be firmly joined to said shaped body of said copper alloy by being subjected to a difiusion causing heat treatment; and subjecting the thus-formed metal-coated unhardened metal body to heat-hardening including heating at a temperature Within the range of between about 350 C. and 600 C. and at which said copper alloy will be heat-hardened and at which diffusion between said copper alloy and said noble metal will take place, thereby firmly adhering said coating of said second metal to said shaped body of said thus-hardened first metal.

References Cited in the file of this patent UNITED STATES PATENTS 1,975,114 Masing et al. Oct. 2, 1934 2,406,683 Hensel Aug. 27, 1946 FOREIGN PATENTS 844,266 Great Britain Aug. 10, 1960 

1. IN A METHOD OF PRODUCING A SHAPED METALLIC BODY OF PREDETERMINED CONFIGURATION, THE STEPS OF SHAPING A HEATHARDENABLE COPPER ALLOY IN UNHARDENED CONDITION, SAID COPPER ALLOY BEING SELECTED FROM THE GROUP CONSISTING OF COPPER-BERYLLIUM ALLOYS, COPPER-SILICON-MANGANESE ALLOYS AND COPPER-SILICON-NICKEL ALLOYS, SO AS TO FORM OF SAID COPPER ALLOY AN UNHARDENED SHAPED BODY OF SAID PREDEERMINED CONFIGURATION; APPLYING TO AT LEAST A PORTION OF THE THUS-FORMED UNHARDENED SHAPED BODY A COATING CONSISTING OF A METAL SELECTED FROM THE GROUP CONSISTING OF GOLD AND GOLD ALLOYS AND ADAPTED TO BE FIRMLY JOINED TO SAID SHAPED COPPER ALLOY BODY BY BEING SUBJECTED TO A DIFFUSION-CAUSING HEAT TREATEMTN; AND SUBJECTING THE THUS-FORMED METAL COATED UNHARDENED COPPER ALLOY BODY TO HEAT-HARDENING INCLUDING HEATING AT A TEMPERATURE WITHIN THE RANGE OF BETWEEN ABOUT 350*C. AND 600* C. AND AT WHICH SAID HEAT-HARDENABLE COPPER ALLOY WILL BE HEAT HARDENED AND AT WHICH SULTANEOUSLY DIFFUSION BETWEEN THE SAME AND SAID METAL WILL TAKE PLACE THEREBY FIRMLY ADHERING SAID METAL COATING TO THE THUS HARDENED COPPER ALLOY BODY. 